System for gas lift

ABSTRACT

Gas is injected into the interior of the production string. The gas eventually reaches a gas lift mandrel that provides access from the interior of the gas lift mandrel to a chamber on the exterior of the gas lift mandrel. The chamber includes a cap that provides gas access between the interior of the chamber and the annulus. However, the cap is fitted with a gas lift valve and a check valve that regulates the gas flow into the fluid.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. patent application Ser. No.16/127,782 that was filed on Sep. 11, 2018 and U.S. Provisional PatentApplication No. 62/557,410 that was filed on Sep. 12, 2017.

BACKGROUND

Generally, when a well is drilled at least one hydrocarbon bearingformation is intersected. Part of the process of completing the wellincludes installing a liner within the well where the liner alsointersects the hydrocarbon bearing formation. Once the liner is inplace, ports are opened up through the liner so that fluids, usually atleast water and oil, may flow from the hydrocarbon bearing formation tothe interior of the liner. Usually, in a newly completed well there issufficient pressure within the hydrocarbon bearing formation to forcethe fluid from the hydrocarbon bearing formation to the surface. Aftersome period of time the pressure gradient drops to the point where thefluid from a hydrocarbon bearing formation is no longer able to reachthe surface.

Once the fluids are no longer able to naturally reach the surfaceartificial lift may be employed. One form of artificial lift is known asgas lift. In a conventional gas lift operation a production tubular isrun into the well. The production tubular is assembled on the surfaceand includes a packer and a number of gas lift mandrels. Each gas liftmandrel has a check valve and a conventional injection pressure operatedgas lift valve.

The production tubular is then run into the well so that the packer maybe set at some point above the ports in the liner to the hydrocarbonbearing formation. Once the packer is set fluid may flow from ahydrocarbon bearing formation into an annular area between the liner andthe production tubular. The packer prevents the fluid from flowing inthe annular area above the packer however the fluid may flow to thebottom of the production tubular and into the production tubular. Oncethe fluid is in the production tubular it may flow upwards to a leveldependent upon the hydrocarbon bearing formation pressure gradient. Thefluid in the production tubular will generally flow up past the annularpacker and will flow upwards past at least one of the gas lift mandrels.Each check valve in the gas lift mandrels prevents the fluid within theproduction tubular from flowing through the gas lift mandrel and intothe annular area above the packer.

In order to begin producing the fluid to the surface high-pressure gas,such as nitrogen, is injected into the annular area between the linerand the production tubular. The only outlet for the high-pressure gas isthrough the gas lift valves into the gas lift mandrels and then into theinterior of the production tubular. As the high-pressure gas reaches agas lift valve the high-pressure gas flows into the gas lift valvethrough ports in the side of the gas lift valve. The ports are locatedbetween the gas lift valve seat and the bellows. The high-pressure gasacts on the bellows adapter and the bellows to compress the bellowswhich in turn lifts the ball off of the seat. With the ball off of theseat the high-pressure gas is able to flow through the seat into thecheck valve. The high-pressure gas then acts upon the check dart tocompress the check dart against the spring and lifting the check dartoff of the check pad allowing the high-pressure gas to flow through thecheck valve and into the gas lift mandrel. As the gas flows out of thegas lift mandrel and into the interior of the production tubularadjacent the gas lift mandrel the high-pressure gas causes the fluid tobecome a froth. The effect is similar to blowing bubbles into milkthrough a straw. The column of fluid which is now froth has a much lowerdensity and therefore a lower head pressure than a pure liquid column.The natural formation pressure in conjunction with the flow of highpressure gas now flowing upward through the production tubular lifts thefroth, and thus the hydrocarbons and other fluid, to the surface.

SUMMARY

In certain operations it has been found advantageous to reverse the flowof injection gas and fluids from the hydrocarbon bearing formation. Inthis instance, again, the production tubular is assembled on thesurface. However in place of the packer and the associated equipment toset the packer a simple plug may be placed on the bottom of the tubular.A number of gas lift mandrels are included in the production tubularassembly.

As noted previously the conventional gas lift mandrel has a port fromthe exterior to the interior of the production tubular. A 90° fitting isplaced on the exterior of the port and is generally welded intoposition. The 90° fitting is threaded so that a check valve may bethreaded into the 90° fitting and the gas lift valve is threaded intothe top of the check valve. High-pressure gas then enters the gas liftvalve, where the high pressure gas flows into the interior of the gaslift valve, then into the check valve, and then into the interior of theproduction tubular through the gas lift mandrel. It is noted that whileother orientations may be utilized generally the 90° fitting is utilizedto allow the check valve or gas lift valve to have an orientation thatis roughly parallel to the mandrel and production tubular. In thecurrent invention however the gas lift mandrel is constructed so thatagain there is a port between the exterior to the interior of theproduction tubular through the gas lift mandrel. A 90° fitting is placedon the exterior of the port and is generally welded into position. Acontainment tube having sufficient length to contain a gas lift valveand a check valve with some room to spare is then attached to the 90°fitting. Again generally by welding. A gas lift valve is then threadedinto the top of a check valve. The check valve is then threaded into acap for the containment tube that allows fluid and gas flowtherethrough. The gas lift valve and check valve are then placed insidethe containment tube in reverse order. I.e. the upper end of the gaslift valve is closest to the 90° fitting with the check valve being onthe other side of the gas lift valve. The through bore fitting is thensecured to the tubular usually by a second set of threads although otherknown arrangements may be utilized. The containment tube cap is gastight to the tubular and the tubular is gas tight to the 90° fitting.

In operation the production tubular is run into the well such that atleast one of the gas lift mandrels are below the surface of the fluidfrom a hydrocarbon bearing formation. The fluid in the annular areabetween the production tubular and the liner is prevented from enteringthe production tubular by the one way check valve, which is now orientedto block the fluid which may reach the check valve from the exterior ofthe gas lift mandrel through the through bore in the containment tubecap.

As noted before a packer is not necessary in this configuration ashigh-pressure gas is run into the interior of the production tubular andis generally prevented from exiting the production tubular by a cap orplug on the end of the production tubular. The exit for thehigh-pressure gas is through the port in the gas lift mandrel throughthe 90° fitting and into the containment tube. The high-pressure gas inthe containment tube then surrounds the gas lift valve where thepressure of the high-pressure gas acts on the bellows and bellowsadapter to raise the ball off of the seat in the gas lift valve therebyallowing the high-pressure gas to flow into and through the gas liftvalve, through the check valve where the gas exits the check valvethrough the containment tube cap, and into the annular area between theliner or casing and the production tubular causing the fluid to become afroth. The fluid which is now froth has a much lower density andtherefore lower head pressure than a pure liquid column. The naturalformation pressure in conjunction with the flow of high-pressure gas nowflowing upward through the annular area lifts the froth, which includeshydrocarbons and other fluid, to the surface. Additionally, by producingthe froth through the annular area between the production tubular andthe liner a much larger cross-sectional flow area as compared to thecross-sectional flow area of the production tubular may be accessed.

Another embodiment of the gas lift system has a mandrel with a port thatallows fluid flow between an exterior and an interior of the mandrel.The mandrel is connected at its upper end and its lower end to aproduction tubular. A containment chamber is connected to the mandrelallowing fluid flow between the port and the exterior of the tubular.The fluid flow is through the containment chamber. The gas lift systemmay include a cap that allows access to the interior of the containmentchamber. The cap allows fluid flow between an interior of thecontainment chamber and the exterior of the mandrel. A gas lift valve iswithin the containment chamber and the gas must pass through the gaslift valve to exit the containment chamber. A check valve is usuallywithin the containment chamber, and the gas must pass through the checkvalve to exit the containment chamber. Typically, the gas flows throughthe check valve only from an interior of the chamber to the exterior ofthe mandrel.

In another embodiment of the gas lift system a gas lift valve isconnected to a production tubular such that gas within the productiontubular may flow from an interior of the production tubular to anexterior the production tubular through the gas lift valve. The gas liftvalve may be within the interior of the production tubular but moreusually the gas lift valve is within a chamber on the exterior of theproduction tubular. The gas lift valve must be attached to the interiorof the production tubular on the surface. The gas lift system alsoincludes a one-way valve allowing gas to flow only from the interior ofthe production tubular to the exterior the production tubular.

Generally, the gas lift system may be used by pressurizing a productiontubular with a gas. Forcing the gas from an interior of the productiontubular to an exterior of the production tubular such that upon exitingthe production tubular the gas enters a containment chamber. The gaswithin the containment chamber then opens a gas lift valve allowing thegas to flow through the gas lift valve and injecting the gas from thegas lift valve into a fluid. The containment chamber is sealed with agas lift valve attached to a cap. The gas lift valve is in the interiorof the containment chamber. The cap allows fluid flow between aninterior of the containment chamber and the exterior of the productiontubular. A check valve is usually located between the gas lift valve andthe cap. When a check valve is included the gas generally passes throughthe check valve to exit the containment chamber. The gas flows throughthe check valve only from an interior of the chamber to the exterior ofthe mandrel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts annular gas injection.

FIG. 2 depicts the system for tubular gas injection.

DETAILED DESCRIPTION

The description that follows includes exemplary apparatus, methods,techniques, or instruction sequences that embody techniques of theinventive subject matter. However, it is understood that the describedembodiments may be practiced without these specific details.

FIG. 1 depicts a prior art system 10 having a liner 12 that intersectsthe hydrocarbon bearing formation 14. A production tubular 16 having apacker 20 has been run into the liner 12 so that the packer 20 is placedat some location above hydrocarbon bearing formations 14. The productiontubular 16 includes a gas lift mandrel 22. The gas lift mandrel 22usually has a recessed area gas lift to reduce the overall diameter ofthe gas lift mandrel 22 and gas lift valve 42. A port 28 allows gasaccess from the exterior of the production tubular 16 to the interior 30of the production tubular 16 through a 90° fitting 26. Check valve 32 isattached to 90° fitting 26 so that fluid in the interior 30 of theproduction tubular 16 is prevented from flowing into the annular area 40between the liner 12 in production tubular 16. Check valve 32 allows gasflow from the annular area 40 to flow through check valve 32 and into90° fitting 26 and further into the interior 30 of the productiontubular 16. A gas lift valve 42 is attached, usually by threads, to theinflow area 33 of check valve 32.

When high-pressure gas, as indicated by arrow 50, is injected into theannular area 40, packer 20 prevents the gas from flowing downwardtowards the hydrocarbon bearing formations 14. In certain instances,packer 20 may be formed by the fluid in the lower portion of the well.The only viable exit for the gas 50 is through port 52 in gas lift valve42. The gas pathway into port 52 is shown by arrow 54. The gas thenflows into the interior portion of gas lift valve 42 into and throughcheck valve 32 into and through 90° fitting 26 and into the interiorregion 30 of the production tubular 16 as indicated by arrow 56. The gasthat enters the interior 30 of the production tubular 16 causes thefluid within the production tubular to froth as indicated by bubbles 60.The froth and high-pressure gas then exit through the production tubularas indicated by arrow 62.

FIG. 2 depicts the current invention where the gas lift system 100 has aliner or casing 112 that intersects hydrocarbon bearing formation 114.The production tubular 116 includes a plug or closed end 120 at somepoint below the gas lift mandrel 122. In some instances the closed end120 may be considered closed due to the presence of fluids at asufficient pressure to prevent the high pressure gas within theproduction tubular 116 from reaching the lower end of the productiontubular 116. The production tubular 116 is run into the liner 112 sothat the gas lift mandrel 122 is at some point below the top of thefluid 123. Generally the gas lift mandrel 122 has a recessed area 124 toreduce the overall diameter of the mandrel and gas lift valve. A port128 allows gas access from the interior 130 of the production tubular116 to the exterior of the production tubular 116 through a 90° fitting126. Gas tight containment tube 170 is attached to 90° fitting 126,typically by welding. A check valve 132 is connected usually by threadsto containment tube cap 133. A gas lift valve 142 is then connected tocheck valve 132 again typically by threads. Containment tube cap 133 isthen threaded into gas tight tubular 170.

High-pressure gas, as indicated by arrow 150, is injected into theinterior region 130 of the production tubular 116. End cap 120 preventsthe high-pressure gas from exiting the production tubular. The only exitfor the high-pressure gas is depicted by arrows 151 and 153 whichindicate the path of the high-pressure gas flow through port 128 whichin turn allows the gas to flow through the 90° fitting around theexterior of the gas lift valve and then into port 152 where the gasenters the interior region of gas lift valve 142. The high-pressure gasacts upon the bellows and stem assembly within gas lift valve 142 toraise the ball off of the seat within gas lift valve 142 allowing thehigh-pressure gas to flow out of gas lift valve into check valve 132 andthen into the annular area 140 where the gas causes the fluid to becomea froth as indicated by bubbles 160. The froth, hydrocarbons, otherfluids, and gas, then proceed to the surface through the annular area140 is indicated by arrow 162. The cross-sectional area of the annulararea 140 is the cross-sectional area of the liner 112 as indicated byarrow 180 less the cross-sectional area of the production tubularindicated by arrow 182. Generally the cross-sectional area of theannular area 140 is greater than the cross-sectional area of theproduction tubular allowing higher fluid flow rates through the annulararea as compared to the production tubular.

While the embodiments are described with reference to variousimplementations and exploitations, it will be understood that theseembodiments are illustrative and that the scope of the inventive subjectmatter is not limited to them. Many variations, modifications, additionsand improvements are possible.

Plural instances may be provided for components, operations orstructures described herein as a single instance. In general, structuresand functionality presented as separate components in the exemplaryconfigurations may be implemented as a combined structure or component.Similarly, structures and functionality presented as a single componentmay be implemented as separate components. These and other variations,modifications, additions, and improvements may fall within the scope ofthe inventive subject matter.

What is claimed is:
 1. A gas lift system comprising; a first mandrelhaving a port that allows gas flow from an interior of the first mandrelto an exterior of the first mandrel, wherein the first mandrel isconnected at its upper end and its lower end to a production tubular, acontainment chamber on the exterior of the first mandrel, a first gaslift valve within the containment chamber, a second mandrel having aport that allows gas flow from an exterior of the second mandrel to aninterior of the second mandrel, wherein the second mandrel does not havea containment chamber, wherein the second mandrel is connected at itsupper end and its lower end to a production tubular, a second gas liftvalve on the exterior of the second mandrel.
 2. The gas lift system ofclaim 1, further comprising a cap, wherein the cap allows access to theinterior of the containment chamber.
 3. The gas lift system of claim 2,wherein the cap allows fluid flow between an interior of the containmentchamber and the exterior of the mandrel.
 4. The gas lift system of claim1, further comprising a gas lift valve within the containment chamber,wherein gas must pass through the gas lift valve to exit the containmentchamber.
 5. The gas lift system of claim 1, further comprising a checkvalve within the containment chamber, wherein gas must pass through thecheck valve to exit the containment chamber.
 6. The gas lift system ofclaim 5, wherein gas flows through the check valve only from an interiorof the chamber to the exterior of the mandrel.